Conventionally, a data transfer processing technique has been provided for transferring data on-line from a given business-use server to a specific memory area without interruption of transactions. When plural memory areas are present as data transfer destinations in the execution of such data transfer, update data are transferred to respective memory areas by two types of schemes including a synchronous scheme (mirror scheme) and a nonsynchronous scheme (background copy scheme).
The synchronous scheme is performed such that during a transaction when data is updated in a memory area in which data updating is executed first, i.e., the memory area serving as a transfer origin, the same data updating is mirrored simultaneously in a memory area serving as a transfer destination. The nonsynchronous scheme is performed such that when data updating is executed in a memory area serving as a transfer origin, update-addresses in a bit-map format, etc., are stored temporarily on a primary memory, and at a given timing, the update is collectively mirrored in a memory area serving as a transfer destination.
The synchronous scheme and the nonsynchronous scheme each have advantages and disadvantages, and therefore need to be used separately for different purposes, depending on transfer conditions and the environment conditions of a transfer origin and a transfer destination. For example, the synchronous scheme has advantages of lighter load on a memory area used as a transfer origin and of immediate reflection of updated data in plural memory areas. The synchronous scheme, on the other hand, has disadvantages in that useless processing increases when the overlap rate of addresses of memories to be updated during the data updating is high, and that data updating may not be reflected correctly affecting transactions when the performance (capacity and access speed) of a memory area serving as a transfer destination is low.
The nonsynchronous scheme has advantages in that update data can be transferred efficiently even when the overlap rate of addresses is high as in the above case, and in that because data is transferred from a memory area serving as a transfer origin to the memory area serving as a transfer destination, a delay in reflecting the data update does not affect transactions even if the performance of a memory area serving as a transfer destination is low. The nonsynchronous scheme, on the other hand, has disadvantages in that load on the transfer origin memory area is heavy, and in that the speed of transferring update data may not match the updating speed. Hence, to transmit a group of update data, a transmission origin selects either the synchronous scheme or the nonscynchronous scheme depending on the contents of the group of update data at each data update, and performs data transfer processing.
According to conventional data transfer processing disclosed in Japanese Patent Application Laid-Open Publication No. 2006-338064, a system administrator, who executes data transfer processing taking into consideration the respective characteristics of the synchronous scheme and the nonsynchronous scheme, must select either of the schemes relying on intuition and experience. In database processing, a general tendency is for data in a group of update data to be written to respective addresses of different areas to lower the overlap rate. In file system processing, on the contrary, an overlap rate tends to be relatively higher. In practice, however, overlap rates vary depending on the contents of the data to be handled, thereby making a definite judgment on overlap rates difficult.
For example, in database processing, access is frequently made to specific metadata in some cases and therefore, the overlap rate of addresses of a group of update data may not be small. In file system processing, on the contrary, the overlap rate is not much larger when data is used mainly as a database table and updated in extensive file offsetting. In this manner, the expectation of a system administrator concerning an overlap rate may be extremely inaccurate even with consideration of general tendencies, thereby leading to a problem of an inefficient data transfer processing.